OIT Measurement of Standard Motor Oils by Pressure DSC

摘要

Oxidation induction time (OIT) is a fast standardized method to characterize the stability of organic materials like polymers and oils against oxygen attack. Pressure DSC is required to increase oxygen concentration for faster reactions at lower temperatures and for the suppression of evaporation of low volatile components. OIT measurements will be compared to standard long time tests. Other comparison is made using the Oxygen Onset Temperature (OOT) method to investigate the influence of oxygen concentration on the start of oxidation during heating of samples of a mineral and a synthetic lubrication oil. The increase of O_2 pressure reduces the onset temperature. The synthetic oil is affected by 36 K, the mineral oil by 33 K about in a similar amount, as the figure below demonstrates. But it is obvious, that the synthetic oils is much more temperature resistant than the mineral oil. This has an impact on the life time of the oils and also is reflected in the selling price of the oils. The measurement parameters must be adapted if small differences between oils have to be analyzed. In such cases, isothermal methods are preferred with a careful selection the temperature.